18186421 has 6 divisors (see below), whose sum is σ = 19990166. Its totient is φ = 16533000.

The previous prime is 18186403. The next prime is 18186431. The reversal of 18186421 is 12468181.

It can be written as a sum of positive squares in only one way, i.e., 12006225 + 6180196 = 3465^2 + 2486^2 .

It is not a de Polignac number, because 18186421 - 2¹³ = 18178229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18186431) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75030 + ... + 75271.

Almost surely, 2^18186421 is an apocalyptic number.

18186421 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18186421 is the 2280-th centered heptagonal number.

It is an amenable number.

18186421 is a deficient number, since it is larger than the sum of its proper divisors (1803745).

18186421 is a wasteful number, since it uses less digits than its factorization.

18186421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150323 (or 150312 counting only the distinct ones).

The product of its digits is 3072, while the sum is 31.

The square root of 18186421 is about 4264.5540212313. The cubic root of 18186421 is about 262.9757768994.

The spelling of 18186421 in words is "eighteen million, one hundred eighty-six thousand, four hundred twenty-one".